CONTENTS

The
aio_write
system call allows the calling process to write
iocb->aio_nbytes
from the buffer pointed to by
iocb->aio_buf
to the descriptor
iocb->aio_fildes.
The call returns immediately after the write request has been enqueued
to the descriptor; the write may or may not have completed at the time
the call returns.
If the request could not be enqueued, generally due
to invalid arguments, the call returns without having enqueued the
request.

If
O_APPEND
is set for
iocb->aio_fildes,
aio_write
operations append to the file in the same order as the calls were
made.
If
O_APPEND
is not set for the file descriptor, the write operation will occur at
the absolute position from the beginning of the file plus
iocb->aio_offset.

If
_POSIX_PRIORITIZED_IO
is defined, and the descriptor supports it, then the enqueued
operation is submitted at a priority equal to that of the calling
process minus
iocb->aio_reqprio.

The
iocb
pointer may be subsequently used as an argument to
aio_return
and
aio_error
in order to determine return or error status for the enqueued operation
while it is in progress.

If the request is successfully enqueued, the value of
iocb->aio_offset
can be modified during the request as context, so this value must not
be referenced after the request is enqueued.

The Asynchronous I/O Control Block structure pointed to by
iocb
and the buffer that the
iocb->aio_buf
member of that structure references must remain valid until the
operation has completed.
For this reason, use of auto (stack) variables
for these objects is discouraged.

The asynchronous I/O control buffer
iocb
should be zeroed before the
aio_write
system call to avoid passing bogus context information to the kernel.

Modifications of the Asynchronous I/O Control Block structure or the
buffer contents after the request has been enqueued, but before the
request has completed, are not allowed.

If the file offset in
iocb->aio_offset
is past the offset maximum for
iocb->aio_fildes,
no I/O will occur.

The following conditions may be synchronously detected when the
aio_write
system call is made, or asynchronously, at any time thereafter.
If they
are detected at call time,
aio_write
returns -1 and sets
errno
appropriately; otherwise the
aio_return
system call must be called, and will return -1, and
aio_error
must be called to determine the actual value that would have been
returned in
errno.

[EBADF]

The
iocb->aio_fildes
argument
is invalid, or is not opened for writing.

[EINVAL]

The offset
iocb->aio_offset
is not valid, the priority specified by
iocb->aio_reqprio
is not a valid priority, or the number of bytes specified by
iocb->aio_nbytes
is not valid.

If the request is successfully enqueued, but subsequently canceled
or an error occurs, the value returned by the
aio_return
system call is per the
write(2)
system call, and the value returned by the
aio_error
system call is either one of the error returns from the
write(2)
system call, or one of: